全文获取类型
收费全文 | 129篇 |
免费 | 11篇 |
国内免费 | 10篇 |
专业分类
化学 | 86篇 |
晶体学 | 1篇 |
力学 | 5篇 |
数学 | 27篇 |
物理学 | 31篇 |
出版年
2023年 | 1篇 |
2022年 | 1篇 |
2021年 | 8篇 |
2020年 | 3篇 |
2019年 | 8篇 |
2018年 | 4篇 |
2017年 | 3篇 |
2016年 | 1篇 |
2015年 | 8篇 |
2014年 | 4篇 |
2013年 | 10篇 |
2012年 | 10篇 |
2011年 | 6篇 |
2010年 | 9篇 |
2009年 | 4篇 |
2008年 | 8篇 |
2007年 | 9篇 |
2006年 | 4篇 |
2005年 | 5篇 |
2004年 | 5篇 |
2003年 | 3篇 |
2002年 | 6篇 |
2001年 | 4篇 |
2000年 | 1篇 |
1999年 | 2篇 |
1998年 | 1篇 |
1997年 | 3篇 |
1996年 | 1篇 |
1995年 | 1篇 |
1994年 | 5篇 |
1990年 | 2篇 |
1987年 | 3篇 |
1986年 | 1篇 |
1984年 | 1篇 |
1983年 | 3篇 |
1979年 | 1篇 |
1908年 | 1篇 |
排序方式: 共有150条查询结果,搜索用时 15 毫秒
101.
Jamel Ben Amara 《Mathematische Nachrichten》2012,285(1):42-46
Oscillation criteria for self‐adjoint fourth‐order differential equations were established for various conditions on the coefficients r(x) > 0, q(x) and p(x). However, most of these results deal with the case when limx → ∞∫x1q(s) ds < +∞. In this note we give a new oscillation criterion in the case when this condition is not fulfilled, in particular when q(x)↗ + ∞ (even with exponential growth). 相似文献
102.
Ghulam Murtza Anjum Weidong Du Rachel Klein Umme Amara Markus Huber‐Lang E. Marion Schneider Peter Wiegand 《Electrophoresis》2010,31(2):309-314
Forensic analysis of mitochondrial displacement loop (D‐loop) sequences using Sanger sequencing or SNP detection by minisequencing is well established. Pyrosequencing has become an important alternative because it enables high‐throughput analysis and the quantification of individual mitochondrial DNAs (mtDNAs) in samples originating from more than one individual. DNA typing of the mitochondrial D‐loop region is usually the method of choice if STR analysis fails because of trace amounts of DNA and/or extensive degradation. The main aim of the present work was to optimize the efficiency of pyrosequencing. To do this, 31 SNPs within the hypervariable regions I and II of the D‐loop of human mtDNA were simultaneously analyzed. As a novel approach, we applied two sets of amplification primers for the multiplexing assay. These went in combination with four sequencing primers for pyrosequencing. This method was compared with conventional sequencing of mtDNA from blood and biological trace materials. 相似文献
103.
Structural,electronic,elastic,and thermal properties of CaNiH_3 perovskite obtained from first-principles calculations
下载免费PDF全文
![点击此处可从《中国物理 B》网站下载免费的PDF全文](/ch/ext_images/free.gif)
S Benlamari H Bendjeddou R Boulechfar S Amara Korba H Meradji R Ahmed S Ghemid R Khenata S Bin Omran 《中国物理 B》2018,(3)
A theoretical study of the structural, elastic, electronic, mechanical, and thermal properties of the perovskite-type hydride CaNiH_3 is presented. This study is carried out via first-principles full potential(FP) linearized augmented plane wave plus local orbital(LAPW+lo) method designed within the density functional theory(DFT). To treat the exchange–correlation energy/potential for the total energy calculations, the local density approximation(LDA) of Perdew–Wang(PW)and the generalized gradient approximation(GGA) of Perdew–Burke–Ernzerhof(PBE) are used. The three independent elastic constants(C_(11), C_(12), and C_(44)) are calculated from the direct computation of the stresses generated by small strains.Besides, we report the variation of the elastic constants as a function of pressure as well. From the calculated elastic constants, the mechanical character of CaNiH_3 is predicted. Pertaining to the thermal properties, the Debye temperature is estimated from the average sound velocity. To further comprehend this compound, the quasi-harmonic Debye model is used to analyze the thermal properties. From the calculations, we find that the obtained results of the lattice constant(a_0), bulk modulus(B_0), and its pressure derivative(B_0') are in good agreement with the available theoretical as well as experimental results. Similarly, the obtained electronic band structure demonstrates the metallic character of this perovskite-type hydride. 相似文献
104.
Ni-containing carbon monoxide dehydrogenases (CODH), present in many anaerobic microorganisms, catalyze the reversible oxidation of CO to CO(2) at the so-called C-cluster. This atypical active site is composed of a [NiFe(3)S(4)] cluster and a single unusual iron ion called ferrous component II or Fe(u) that is bridged to the cluster via one sulfide ion. After additional refinement of recently published high-resolution structures of COOH(x)-, OH(x)-, and CN-bound CODH from Carboxydothermus hydrogenoformans (Jeoung and Dobbek Science 2007, 318, 1461-1464; J. Am. Chem. Soc. 2009, 131, 9922-9923), we have used computational methods on the predominant resulting structures to investigate the spectroscopically well-characterized catalytic intermediates, C(red1) and the two-electron more-reduced C(red2). Several models were geometry-optimized for both states using hybrid quantum mechanical/molecular mechanical potentials. The comparison of calculated Mo?ssbauer parameters of these active site models with experimental data allows us to propose that the C(red1) state has a Fe(u)-Ni(2+) bridging hydroxide ligand and the C(red2) state has a hydride terminally bound to Ni(2+). Using our combined structural and theoretical data, we put forward a revised version of an earlier proposal for the catalytic cycle of Ni-containing CODH (Volbeda and Fontecilla-Camps Dalton Trans. 2005, 21, 3443-3450) that agrees with available spectroscopic and structural data. This mechanism involves an abnormal CO(2) insertion into the Ni(2+)-H(-) bond. 相似文献
105.
Hasna Jerbi Mourad Hidouri Mohamed Rzeigui Mongi Ben Amara 《Acta Crystallographica. Section C, Structural Chemistry》2011,67(3):i17-i20
A new phosphate, sodium calcium magnesium tetrakis(phosphate), Na8Ca1.5Mg12.5(PO4)12, has been synthesized by a flux method. Its novel structure consists of MgOx (x = 5 and 6) polyhedra and MO7 (M = Mg or Na) octahedra linked directly through common corners or edges to form a rigid three‐dimensional skeleton, reinforced by corner‐sharing between identical Mg12MO48 units. The connection of these units by the PO4 tetrahedra induces cavities and crossing tunnels where the Na+ and Ca2+ cations are located. This structural model was supported by a 31P NMR spectroscopy study which confirmed the existence of 12 crystallographically independent sites for the P atoms. 相似文献
106.
107.
The relative rates of H-transfer between partners in ion-neutral complexes were compared with those in intramolecular rearrangements using results of first differential photoionization mass spectrometry measurements. Complex-mediated H-transfers are inferred to have rates of the same order as those for intramolecular hydrogen rearrangements, suggesting a similar range of motion of the reactive sites in both types of reactions. It is also concluded that at their fastest H-transfers take place between the partners in ion-neutral complexes within at most the time of several rotations of the partners in the complexes. Copyright 1999 John Wiley & Sons, Ltd. 相似文献
108.
M. Amara R. M. Gal ra P. Morin T. Veres P. Burlet 《Journal of magnetism and magnetic materials》1994,130(1-3):127-132
Among the AuCu3-type RIn3 series where R is a rare earth, the NdIn3 compound presents a complex magnetic phase diagram. In this compound, which orders antiferromagnetically at TN = 5.9 K, three magnetic phases are separated by two sharp first-order transitions. The phase diagrams, determined for the main crystallographic directions, by magnetization measurements in fields up to 7 T show a strong dependence of the transition temperatures. In order to determine the actual magnetic structures in NdIn3, a neutron diffraction experiment has been performed on a single crystal under magnetic field. It shows that the magnetic structures are collinear (single q) with the magnetic moments aligned along the fourfold axis. They clearly evidence the existence of two incommensurate phases with q = (1/2, 1/2, τ): for TN T 5.5 K, τ1 ≈ 0.037 2π/a and the structure is sine-wave modulated, for 5.5 K > T > 4.7 K, τ2 = 0.017 2π/a and the structure squares up. Below 4.7 K the q = (1/2, 1/2, 0) commensurate structure is stabilized. 相似文献
109.
110.
This paper deals with a posteriori estimates for the finite element solution of the Stokes problem in stream function and vorticity formulation. For two different
discretizations, we propose error indicators and we prove estimates in order to compare them with the local error. In a second
step, these results are extended to the Navier-Stokes equations.
Received March 25, 1996 / Revised version received April 7, 1997 相似文献